1. Field of the Invention
The present invention generally relates to an image forming system comprising an image forming apparatus for forming an image on sheet such as paper, and a post-processing apparatus for performing post-processing on the sheet having the image formed thereon. More particularly, the present invention relates to a technology for binding a sheet bundle formed of a plurality of sheets having an image formed thereon.
2. Description of the Related Art
Image forming systems may include a post-processing apparatus for performing various kinds of post-processing on a sheet having an image formed thereon by an image forming apparatus. As this type of post-processing apparatus, for example, there is known a sheet binding processing apparatus including a stapler for binding a sheet bundle formed of a plurality of sheets through a use of a binding member such as a metal staple.
In a sheet binding processing apparatus, generally, the sheet bundle delivered from the image forming apparatus is automatically bound by the stapler (“automatic stapling”). On the other hand, there is a demand to bind the sheet bundle through a manual operation by a user (“manual stapling”) instead of the automatic stapling.
To meet the users' demand as described above, U.S. Pat. No. 7,407,156 discloses such a technology that the user manually inserts the sheet bundle through a delivery port of the post-processing apparatus, to thereby bind the sheet bundle with the stapler.
When the manual stapling as described above is performed, however, binding process may be performed in a state that the sheet bundle is not arranged in a correct binding position. In that case, the binding member which has failed to bind the sheet bundle in a correct manner may remain in the sheet binding processing apparatus. The binding member having remained in the sheet binding processing apparatus may be pushed into the sheet binding processing apparatus along with the sheet bundle at the next binding process, which may be a cause of the breakdown of the sheet binding processing apparatus.